1. Field of the Invention
The invention relates to a panoramic viewing apparatus having an imaging system that is arranged in a housing provided with a rotary drive, the imaging system having a lens system by means of which the images of the objects are imaged on a detector after passing through the lens system, and there being provided in the beam path for the purpose of compensating the image motion caused by the rotation a counter-motion device that produces during the imaging time a motion directed at least approximately synchronously against the rotations produced by the rotary drive.
2. Description of the Related Art
Panoramic viewing apparatuses that can observe the entire angular range of 360 degrees are much used for the purposes of control, monitoring or observation, for example on boat masts. However, blurred images are produced because the section of the visual field varies during the recording time or exposure owing to the rapid rotation of the apparatus.
In order to avoid this image motion, the rotary movement has so far been abruptly stopped at the moment of recording in the case of conventional panoramic viewing units. The sensor head or the entire panoramic viewing unit remains stationary during exposure and then rotates further jerkily until the next recording is made.
However, this conventional method of timing is problematic as regards the technical realization, because a large mass, specifically as a rule the complete panoramic viewing apparatus, must be quickly accelerated and abruptly braked again. This method has proved to be very expensive and subject to faults.
As an alternative, therefore, there are also known panoramic viewing apparatuses in the case of which the rotary movement of the apparatus or of the housing is constant. Provided in the interior of the housing is a counter-motion device by means of which the image motion caused by the rotation is compensated at the moment of recording. A so-called descanning mechanism is talked of here. The known descanning devices are arranged in the afocal or parallel beam path.
Several variants of descanning mechanisms that are arranged in the afocal or parallel beam path are described in this context in U.S. Pat. No. 5,663,825. A mirror is used that is moved against the rotary movement of the panoramic viewing unit during the imaging time.
U.S. Pat. No. 5,338,933 discloses a descanning device in the case of which there is provided for descanning a mirror that rotates during the exposure in a direction opposite to the viewing head, and jumps back quickly into its initial position after the recording of an image, in order to repeat the operation during the exposure for the next image. The mirror is likewise arranged in the afocal or parallel beam path.
However, arranging the known descanning device in the afocal or parallel beam path necessitates a relatively large mirror, because the width of the parallel beam path requires a corresponding size. Because of the large masses resulting therefrom that are to be accelerated, these counter-motion devices are likewise very complicated to produce and relatively susceptible to disturbance in operation. Moreover, there is a spacing between the parallel beam path and the detector, because there is a need here firstly also to provide at least one additional lens in order to image these objects on the detector.